Looks like someone has already subbed, so it should show up now, but essentially you just manually put in the url and go there. for example this page on kbin is https://kbin.social/m/nostupidquestions@lemmy.world, just change that to https://kbin.social/m/flyfishing@lemmy.world and subscribe with a kbin account.
Turns out there is a few other ways to do it as well, this stack exchange post should have some more information if you want it.
On kbin here, definitely can see them. If they did not federate with kbin that means they just can’t see kbin posts/comments